This significant drop in SOX emissions is due in large part to government actions to fight acid rain, and related federal-provincial and United States agreements on capping SOX emissions by 1994. Reductions were also realized through technological upgrades and new air pollution controls for non-ferrous metal smelters. Decreases also occurred due to reductions in emissions from fossil-fuel-fired (e.g., coal-fired) power-generating utilities, plant closures, as well as a reduction in emissions from the petroleum refining sector. Further emissions reductions were achieved through the implementation of low-sulphur fuels.